Rapid determination of enzyme purity by a microdialysis-based assay

Microdialysis was shown to be useful as a fast on-line sampling method for determining the purity of starch hydrolysing enzymes. The enzymes were char acterised using their hydrolytic properties. beta-Amylases and pullulanases from different sources and/or manufacturers were investigated, with maltos e, maltoheptaose, pullulan, and potato amylopectin starch (PAP) as substrat es. The hydrolysis products were sampled via an on-line microdialysis probe and determined in a high-performance anion-exchange chromatographic (HPAEC ) system. Comparison between the expected (theoretical) hydrolysis products with those obtained in the experiments made it possible to determine impur ities in the enzymes. Two of the beta-amylases and one pullulanase released unwanted hydrolysis products, indicating trace impurities in the enzyme pr eparation. Microdialysis sampling allows on-line sampling and eliminates se parate sample preparation and clean-up steps. On-line microdialysis coupled to a HPAEC system is therefore a fast and simple technique for analysing e nzyme hydrolysates.